Have you ever felt that the very title, Progress in Optics, conjured an image in your mind? Don’t you see a row of handsomely printed books, bearing the editorial stamp of one of the most brilliant members of the optics community, and chronicling the field of optics since the invention of the laser? If so, you are certain to move the bookend to make room for Volume 16, the latest of this series. It contains seven chapters on widely diverging topics, written by well-known authorities in their fields. These are: 1) Laser Selective Photophysics and Photochemistry by V. S. Letokhov, 2) Recent Advances in Phase Profiles (sic) Generation by J. J. Clair and C. I. Abitbol, 3 ) Computer-Generated Holograms: Techniques and Applications by W.-H. Lee, 4) Speckle Interferometry by A. E. Ennos, 5 ) Deformation  Invariant, Space-Variant Optical  Pattern Recognition by D. Casasent and D. Psaltis, 6) Light Emission from High-Current Surface-Spark Discharges by R. E. Beverly, and 7) Semiclassical Radiation  Theory within a  QuantumMechanical Framework by I. R. Senitzkt. The  breadth of topic  matter  spanned  by  these  chapters makes it impossible, for this reviewer at least, to pass judgement on the comprehensiveness, relevance, and completeness of every chapter. With an editorial board as prominent as that of Progress in Optics, however, it seems hardly likely that such comments should be necessary. It should certainly be possible to take the authority of each author as credible. The only remaining judgment to be  made on these chapters is their readability. In short, what are they like to read? The first sentence of the first chapter greets the eye with an obvious typographical error: “The creation of coherent laser light source, that have tunable radiation, opened the . . . .” Two pages later we find: “When two types of atoms or molecules of different isotopic composition ( A and B ) have even one spectral line that does not overlap with others, it is pos-

Progress in optics

Phase conjugation by stimulated Brillouin scattering represents a fundamentally promising approach for achieving power scaling of solid-state lasers. Following a summary of the power scaling problem and an overview of phase conjugation concepts, a review is presented of the application of phase conjugation to solid-state lasers. The author describes power scaling using demonstrated techniques for compensating static and thermally induced aberrations and depolarizations, as well as energy scaling by coherent coupling of multiple-gain media. Applications to diode-pumped lasers are discussed, as is a novel approach for power scaling of diode lasers themselves. Future research directions are indicated regarding conjugation fidelity at increasingly higher energies or with short-pulse and/or broadband lasers. >

A review of phase-conjugate solid-state lasers

The physics of optical vortices, also known as twisted light, is now a well-established and a growing branch of optical physics with a number of important applications and significant inter-disciplinary connections. Optical vortex fields of widely varying forms and degrees of complexity can be realised in the laboratory by a host of different means. The interference between such beams with designated orbital angular momenta and optical spins (the latter is associated with wave polarisations) can be structured to conform to various geometrical arrangements. The focus of this review is on how such tailored forms of light can exert a controllable influence on atoms with which they interact. The main physical effects involve atoms in motion due to application of optical forces. The now mature area of atom optics has had notable successes both of fundamental nature and in applications such as atom lasers, atom guides and Bose–Einstein condensates. The concepts in atom optics encompass not only atomic beams interacting with light, but atomic motion in general as influenced by optical and other fields. Our primary concern in this review is on atoms in structured light where, in particular, the twisted nature of the light is made highly complex with additional features due to wave polarisation. These features bring to the fore a variety of physical phenomena not realisable in the context of atomic motion in more conventional forms of laser light. Atoms near resonance with such structured light fields become subject to electromagnetic fields with complex polarisation and phase distributions, as well as intricately structured intensity gradients and radiative forces. From the combined effect of optical spin and orbital angular momenta, atoms may also experience forces and torques involving an interplay between the internal and centre of mass degrees of freedom. Such interactions lead to new forms of processes including scattering, trapping and rotation and, as a result, they exhibit characteristic new features at the micro-scale and below. A number of distinctive properties involving angular momentum exchange between the light and the atoms are highlighted, and prospective applications are discussed. Comparison is made between the theoretical predictions in this area and the corresponding experiments that have been reported to date.

https://iopscience.iop.org/article/10.1088/2040-8986/aaed14/pdf

Atoms in complex twisted light

When a Brillouin-shifted signal interacts with a two strong counterpropagating pump beams in a Brillouin active medium, a conjugate field will grow exponentially in time until it depletes the power of the pump beams and hence produce very high reflectivities (>10/sup 6/). The technique can be used to conjugate very weak signals ( >

A review of Brillouin-enhanced four-wave mixing

Optical nanofibres are increasingly being used in cold atom experiments due to their versatility and the clear advantages they have when developing all-fibred systems for quantum technologies. They provide researchers with a method of overcoming the Rayleigh range for achieving high intensities in a focussed beam over a relatively long distance, and can act as a noninvasive tool for probing cold atoms. In this review article, we will briefly introduce the theory of mode propagation in an ultrathin optical fibre and highlight some of the more significant theoretical and experimental progresses to date, including the early work on atom probing, manipulation and trapping, the study of atom-dielectric surface interactions, and the more recent observation of nanofibre-mediated nonlinear optics phenomena in atomic media. The functionality of optical nanofibres in relation to the realisation of atom-photon hybrid quantum systems is also becoming more evident as some of the earlier technical challenges are surpassed and, recently, several schemes to implement optical memories have been proposed. We also discuss some possible directions where this research field may head, in particular in relation to the use of optical nanofibres that can support higher-order modes with an associated orbital angular momentum.

/pdf/optical-nanofibres-and-neutral-atoms-rjm8e91jvk.pdf

Optical nanofibres and neutral atoms

Cold matter trapping via slowly rotating helical potential

The rotational Doppler shift of a photon with orbital angular momentum ±lℏ is shown to be an even multiple of the angular frequency Ω of the reference frame rotation when the photon is reflected from the phase-conjugating mirror. The one-arm phase-conjugating interferometer is considered. It contains N Dove prisms or other angular-momentum-altering elements rotating in opposite directions. When such interferometer is placed in the rotating vehicle, the δω=4(N+1/2)l·Ω rotational Doppler shift appears. As a result, the helical interference pattern will rotate with angular frequency δω/2l. The accumulation of angular Doppler shift via successive passages through the N image-inverting prisms is due to the phase conjugation; for a conventional parabolic retroreflector, the accumulation is absent. The features of such a vortex phase-conjugating interferometry at the single-photon level are discussed.

Rotational Doppler shift of a phase-conjugated photon

The previously unknown property of the optical speckle pattern reported. The interference of a speckle with the counterpropagating phase-conjugated (PC) speckle wave produces a randomly distributed ensemble of a twisted entities (ropes) surrounding optical vortex lines. These entities appear in a wide range of a randomly chosen speckle parameters inside the phase-conjugating mirrors regardless to an internal physical mechanism of the wave-front reversal. These numerically generated interference patterns are relevant to the Brillouin PC mirrors and to a four-wave mixing PC mirrors based upon laser trapped ultracold atomic cloud.

/pdf/twisted-speckle-entities-inside-wave-front-reversal-mirrors-4432qsj0vg.pdf

Twisted speckle entities inside wave-front reversal mirrors

The usage of vortex-labyrinth fields and Talbot lattices as optical dipole traps for neutral atoms is considered for the wavelength of trapping radiation in the range 0.98–2.79 µm. The square vortex lattices generated in high Fresnel number solid-state microchip lasers are studied as a possible realization. The distribution of light field is obtained via a nonstationary computational model based on Maxwell–Bloch equations for a class-B laser, discrete Fox–Lee map with relaxation of inversion and a static model based on superposition of copropagating Gaussian beams. The spatial patterns obtained numerically and observed experimentally previously are interpreted as nonlinear superposition of vortices with helicoidal phase dislocations. The distribution of light field is approximated analytically by a sum of array of vortex lines and an additional parabolic subtrap. The separable optical trapping potential is proposed with similar intensity distribution. The factorization of the macroscopic wavefunction has ...

/pdf/3d-vortex-labyrinths-in-the-near-field-of-solid-state-108cpwmfl6.pdf

A. Yu. Okulov

Papers

Cold matter trapping via slowly rotating helical potential

Rotational Doppler shift of a phase-conjugated photon

Twisted speckle entities inside wave-front reversal mirrors

3D-vortex labyrinths in the near field of solid-state microchip laser

Phase fluctuations of the Stokes wave produced as a result of stimulated scattering of light